Process for obtaining products of great value, easily and rapidly, by electrolytic means



Patented July 2, 1935 PROCESS m OBTAINING rnonuc'rs or GREAT VALUE,EASILY AND narmnr, BY ELECTROLYTIC MEANS Hermann Kuppel and France,assignors to Louis Simeant, Clichy, Socit a Responsabilit Limite Kuppel& Simeant, Clichy, France No Drawing. Application May 2, 1933, SerialNo. 669,066. In France August 11, 1932 3 Claims.

The object of'the present invention is a new process which makes itpossible to obtain products of irreproachable quality with greatfacility and under particularly advantageous conditions.

It applies more particularly, but not exclusive- 1y, to the obtainmentof entirely polished metals, alloys and metallic deposits, thecharacteristics of which are far superior in every respect to those ofthe products obtained by the processes at present known.

The new process is based on the fact, as ascertained by the petitioners,that the tension applied to electrolytes not only exerts a considerableinfluence on the behavior of the electrolyte but also brings about aprofound modification in the very nature of the electrolyte.

In usual practice the tension applied to the electrolytes is onlyslightly greater than the tension of decomposition, said tension ofdecomposition being determined on the one hand by the resistivity of theelectrolyte under consideration and on the otherhand by thecounterelectromotive iorce'oi polarization.

According to the recognized principles the amount of the tension to beemployed is particularly well defined in the work published in France in1930under'the title Llectro deposition des mtaux by Dr. W. Pfanhauser,translated by A. Alleman, N. Gourot and J. Fregier.

In this work which is one of the most carefully studied and mostcomplete on the subject, the author indicates, as regards the relationbetween density and tension (page 94 and following pages), how one candetermine said tension in practice and he adds (page 117) that the fact01' raising this tension would be detrimental since, as the densityincreases at the same time, maximum density would be exceeded.

It is not therefore only through reasons of economy that only tensionsreduced to a minimum have been employed up to the present but alsobecause of material impossibility.

Indeed the increase in tension, consequently the increase in the densityof the current, causes considerable disadvantages which professionals inthe science have seemed to consider 'as an impassable barrier up to thepresent.

Now the petitioners have establishedthe surprising and unexpected factthat if one persistently increases the tension a moment arrives wherethe known disadvantages are not only reduced but actually disappearcompletely over a certain period in the course of which the resultsobtained are better.

It next happens that the disadvantages reappear then disappear again ifthe tension is further increased and so on.

After a number 01' tests the petitioners noticed that this periodicityin the recurrence of the disadvantages was due to the fact that, as the5 temperature increases considerably, said temperature is no longer innormal relation to the tension and to the density of the current inrespect of the composition of the electrolyte.

Therefore, 'in order to benefit by the advanl0 tages obtainable, it wasnecessary to endeavor to remain within a period of favorable operation.

It was then that the petitioners established a second fact: after havingincreased the tension to the suitable point if it be then diminished 5down to a point where the temperature remains stable it so happens,automatically and without any intervention, that the density of thecurrent tends, to reach a maximum while the tension tends to reach aminimum. These two new 2 values would appear to depend only on thecomposition of the electrolyte.

The density of the current will then be far greater than normal and thetension will be greater than normal tension to the extent of some volts.

This indicates that the nature of the electrolyte has become completelymodified during the period of increased tension to which it has beensubmitted temporarily.

Indeed the fact may be very easily ascertained in certainv cases. Forinstance it one watches a solution of copper sulphate to which theaforementioned treatment is applied one will observe the appearance of aparticular phenomenon commencing at a certain tension.

A circulation, syrupy in appearance, will be set up and will at firstcommence to flow along the anode or anodes, it will then form, at thebottom of the vat, sheets possessed of an alternating movement from thebottom upwards and vice versa, it will then tend. toflow upward alongthe cathode or to tum'with said cathode. It is from this moment onwardthat the density of the current increasesand that the tension tends todrop.

There is therefore reason to assume that this circulation constitutes aparticularly conductive path along which move extremely minute'metallicparticles. Moreover one notices that, not- 50 withstanding the highdensity of the current, variations in the distance between theelectrodes have no appreciable effect on the tension.

It is remarkable to note that that portion or the'liquid which is thuscaused to circulate pos- 55 current will have reached sesses interestingproperties. It seems to oppose, in a perfect manner, the gaseousdischarge which so frequently sets up the formation of spots andirregularities on the cathode. Moreover the oscillating sheets remain ata constant level if the working conditions of the electrolyte remainstable.

If the horizontally rotating cathode be replaced by a cathode of adiameter less than that of the former one will notice, between the newcathode and the oscillating sheets, a clearer layer which does notoppose the gaseous discharge.

By operating as at the commencement the level of the oscillating sheetswill rise, the clear layer will disappear and the normal process will beresumed as soon as the level of the sheets reaches the new cathode.

A similar phenomenon occurs after a prolonged stop in working, the levelof the sheets drops, the sheets may indeed disappear completely.

They can be caused to reappear by proceeding in the same manner aspreviously.

It has-been noted also that difierent metals can be deposited at thesame time without having to modify the composition of the original bath.

In the case of copper for instance if, after treating the electrolyteaccording to the process of the invention, chromium anodes arepositioned alongside the copper anodes it will be noticed at once thatthe electrolyte changes color, passing from blue to green, and an alloyof copper and chromium is obtained at the cathode without any difficultyand without having to change the working of the electrolysis.

In order to apply the process which forms the subject matter of theinvention it should however be bome in mind that it is necessary toobtain absolute automaticity and that, under these conditions, separateexcitation generators should be employed, the regulating of the tensionbeing obtained by acting on the excitation and not by means of a bathrheostat which has,v so far, been considered as indispensable.

Control instruments should excitation circuit for, in actual practice,the indications supplied by said instruments will make it possible toregulate working conditions with certainty.

It is of'course understood that, under the conditions of the operation,the size of the vats must be determined by taking into account thedensity of the current it is possible to obtain and taking into accountalso the diflerences in temperature due to outside influences(surrounding temperature, temperature oi. premises heated in winter,etc).

The putting into practice of the process as set forth hereinabove iseffected as follows: whatever the composition of the electrolyte may be,the tension is progressively increased to 2, 3, 4, 5, 6, 8, 10 tc.,volts and this is done until the moment when it is ascertained that theresulting intensity of the electrode circuit continues to increasewhereas the tension itself tends to drop.

As this coincides with a marked elevation in the temperature of theelectrolyte, the tension is then progressively reduced until thetemperature of the electrolyte remains stable.

After a short while the tension will have reached its minimum and thedensity of the its maximum. The electrolytic process will then beperfectly estab: lished and the products obtained will be of rebe placedon the markable quality in' respect of outside aspect, structure, purityand mechanical characteristics.

This process is particularly efficient when it is utilized inconjunction with smoothing devices acting in the manner described inGerman Patent No. 480,420 delivered-May 18, 1926 and correspondingFrench Patent No. 628,300 of November 4, 1926.

As an example this is the application of the process for the purpose ofobtaining an electrolytic copper pipe of about 125 square decimeters inlateral surface in a bath comprising no substance other than water with24% of copper sulphate and preferably very little acid, at an initialtemperature of centigrade. By acting on the excitation the tension ofthe generator is brought up successively to 2, 4, 6, 8, 10, 12, 14volts. Total corresponding intensities of 100-200- 300-500-800 amperesare obtained.

When 14 volts is reached, the tension will show a tendency to drop andthe intensity will rise, the temperature will increase rapidly.

The excitation will then be acted upon in the reverse way to drop thetension progressively and to maintain the temperature until the momentwhen said temperature increases no further, which will occur in theneighborhood of 45 to 50 centigrade.

The tension will thus have been stabilized at 6 or 8 volts and theintensity at 1100 or 1200 amperes which will remain the stable workingconditions under which it will be possible to obtain without anyinconvenience a faultless deposit, polished, very fine in grain,possible, if it is so desired, to compose an alloy by adding anodes ofthe metal selected.

The supplementary expenditure in energy owing to the tension employed isamply compensated by the quality and the value of the product obtainedas well as by the economy eflected, on the other hand, by the absence ofspecial products, the absence of auxiliary heating and the absence ofdevices for stirring the electrolyte.

The micrographic examination of a thick tube obtained by the processwhich forms thesubject matter of the invention reveals extraordinaryfineness of the grain.

In addition the mechanical characteristics of the metal constitutingsuch a'tube show the coexistence of great hardness and high resistanceto breakage and great elongation as well as very great malleability.Chemical analysis shows its Purity.

This clearly indicates the great value of the product obtained. Itshould be noted, in addition, that the tube has emerged from theelectrolytic bath completely finished and polished without having toundergo any treatment or subsequent mechanical polishing. In the case ofplates or cylinders intended for heliographic engraving or similarpurposes,- a light coal polishing may be effected if necessary.

It has been possible to obtain, in the same manner and with equalfacility, deposits of iron, zinc and aluminum as well as alloys ofhandsome outside appearance, the physical and mechanical properties ofwhich are distinctly superior to those of the products known to date.

What we claim is:

1. In the process of depositing from a coppercontaining electrolyticbath, comprising progressively raising the voltage and consequently thecurrent density in condition is reached where the current density theelectrode circuit until a continues to increase of its own accordwhereas the voltage tends to decrease, progressively decreasing thetension down to a point where the temperature of the electrolyte isstabilized, and thereafter operating the electrolytic bath during thedeposition process at the voltage and current density thus established.

.2. In the process of depositing from a coppercontaining electrolyticbath, comprising progressively raising the voltage and consequently thecurrent density in the electrode circuit until a condition is reachedwhere the current density continues to increase of its own accordwhereas the voltage tends to decrease, progressively decreasing thetension down to a point where the temperature of the electrolyte isstabilized, thereafter operating the electrolytic bath during thedeposition process at the voltage and current density thus established,and maintaining the temperature 01' the electrolyte substantiallyconstant throughout the process.

3. An electrolytic process for the deposition of copper from acopper-containing solution, including the step of raising. theelectromotive force at the electrodes so as to increase the currentintensity therebetween until the said intensity tends to riseautomatically simultaneously with decrease of electromotive force, andthen pro-- gressively decreasing the electromotive force to a point atwhich the temperature of the electrolyte becomes stabilized.

- HERMANN KUPPEL.

LOUIS SIMEANT.

